This invention relates generally to gas turbine engine variable stator vane assemblies and, more particularly, to bushings used within the variable stator vane assembly.
Gas turbine engines include a high pressure compressor, a combustor, and a high pressure turbine. The high pressure compressor includes a rotor, and a plurality of stages. The rotor is surrounded by a casing, and each stage includes a row of rotor blades and a row of stator vanes. The casing supports the stator vanes, and the rotor supports the rotor blades. The stator vane rows are between the rotor blade rows and direct air flow toward a subsequent downstream rotor blade row. Furthermore, because at least some known gas turbine engines include water injection systems to facilitate reducing operating engine temperatures, the stator vane rows are exposed to a water/air mist mixture.
Variable stator vane assemblies are utilized to control the amount of air flowing through the compressor to facilitate optimizing performance of the compressor. Each variable stator vane assembly includes a variable stator vane which extends between adjacent rotor blades. The variable stator vane is rotatable about an axis such that the stator vane is positionable in a plurality of orientations to direct air flow through the compressor.
At least some known variable vane assemblies include a variable vane, a bushing, and a spacer. The bushing extends between the variable vane and the casing, and between the spacer and the casing, to prevent both the spacer and the vane from contacting the casing. Because of wear considerations, the bushings are typically fabricated from materials having high durability and low friction. However, because the variable stator vane assembly is exposed to the water/air mixture, to minimize corrosion and oxidation, the bushings are also typically fabricated from non-metallic materials.
In an exemplary embodiment, a variable stator vane assembly for a gas turbine engine includes a bushing that facilitates extending a useful life of the variable stator vane assembly. The stator vane assembly includes a spacer and a vane secured to an engine casing. The bushing is between the spacer and vane, and prevents the spacer and the vane from contacting the engine casing. The bushing is fabricated such that at least a portion of the bushing is electrically conductive.
During operation, as the engine operates, a water/air mixture flowing through the engine may cause a static electrical charge to develop on metallic components of the variable stator vane assembly. Because the bushing is fabricated such that at least a portion of the bushing is electrically conductive, a conducive path is realized through the bushing, such that electrical charges induced within the variable stator vane assembly are discharged through the bushing to ground. As a result, the bushing facilitates reducing or eliminating electrical charges within the variable stator vane assembly in a cost effective and reliable manner.